Solvent- and metal-free upcycling of low-density polyethylene using a practical ZSM-5/Al2O3 bead catalyst

Upcycling plastic waste into valuable resources without solvents, precious metals, or additional H2 under mild conditions is a formidable challenge that requires new innovations. Herein, we document a catalyst based on Al2O3 beads and zeolite ZSM-5 (ZSM-5#Al2O3(2 h)). It cracked polyethylene (PE) into gasoline-range C4 − C12 hydrocarbons with a selectivity of 98% and a yield of >71% within 1.5 h at 260 °C. Characterization of the catalysts revealed a mesoporous structure and suitable Brønsted acid sites, which promoted the diffusion and catalytic activation of PE. Adjusting the dosage of zeolite supported on Al2O3 beads enables regulation of both the number and strength of acidic sites. Theoretical calculations confirmed that the interfacial interaction between zeolite ZSM-5 and Al2O3 reduces the acid strength of the composite. This is beneficial for the formation of higher hydrocarbons. Remarkably, the process was performed in a 1 L CSTR unit. These results provide instructive guidance for the design of high-performance catalytic materials used in PE waste recycling. Upcycling plastic waste into valuable resources without solvents, precious metals, or additional H2 under mild conditions has remained challenging. Here, the authors report a catalyst based on Al2O3 beads and zeolite ZSM-5 for the conversion of polyethylene into gasoline-range C4 − C12 hydrocarbons with a selectivity of 98% and yields of > 71% within 1.5 h at 260 °C.